Download Association Bulletin #14-05 - Babesiosis

Association Bulletin #14-05
Date: July 18, 2014
To: AABB Members
From: Graham Sher, MD, PhD – President
Miriam A. Markowitz – Chief Executive Officer
Re:
Babesiosis
Summary
This bulletin was developed by the AABB Transfusion Transmitted Diseases (TTD) Committee’s
Babesia and Other Tick-Borne Diseases Work Group to provide educational materials and
recommendations regarding: 1) the epidemiology of Babesia infection and babesiosis case reports,
including transfusion-transmitted babesiosis (TTB); 2) clinical manifestations of babesiosis and
those patients/recipients at greatest risk; 3) diagnosis and treatment of babesiosis; 4) managing
potential TTB including case investigation and look-back; and 5) measures to mitigate the risk of
TTB. A listing of critical unresolved issues is provided to emphasize topics that require further
discussion. This bulletin supersedes Association Bulletin #09-06, “Transfusion-Transmitted
Babesia.”
Association Bulletins, which are approved for distribution by the AABB Board of Directors, may
include announcements of standards or requirements for accreditation, recommendations on
emerging trends or best practices, and/or pertinent information. This bulletin contains educational
information and recommendations for investigating and decreasing the risk of TTB. These
recommendations do not represent requirements for accreditation.
Background
Babesia spp. are obligate intraerythrocytic protozoan parasites that are the etiologic agents of
babesiosis, a potentially life-threatening, malaria-like illness in humans.1 More than 160 cases of
TTB have been recognized in the United States, contributing to at least 28 associated deaths in the
30 years from 1979 to 2009.2 In the US, B. microti is the primary agent of human babesiosis,
accounting for almost all of the documented cases of transfusion transmission, and is, therefore,
the focus of this bulletin.3 In recent years, documented TTB cases have increased (i.e., three
quarters of cases have occurred since 2000), reflecting the fact that B. microti is an emerging agent
with an expanding geographic distribution and enhanced recognition and reporting.
TTB is the leading infectious cause of mortality (38%) in transfusion recipients as reported to the
Food and Drug Administration (FDA).4 The AABB Emerging Infectious Diseases (EID) subgroup
of the TTD Committee categorized Babesia as a high priority agent for the development and
implementation of an intervention to reduce the incidence of TTB.5 However, the only approach
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currently implemented to reduce the transfusion risk is a largely ineffective donor interview
question regarding a history of babesiosis.6 There are no FDA-licensed donor screening tests, but
selective testing with serologic and molecular tests is proceeding under investigational new drug
(IND) protocols in some areas. TTB cases continue to be associated with blood products not tested
under IND protocols. Appendix A contains an updated discussion of the epidemiology of Babesia
infection.
Babesiosis Case Reports
The expanding geographic range of B. microti, increasing incidence of babesiosis, and the threat
to the blood supply led the Council of State and Territorial Epidemiologists (CSTE) to designate
babesiosis as a nationally notifiable disease in 2011,7 although not all states have made it a
reportable condition as yet. The clinical case definition for babesiosis takes into consideration
transfusion for purposes of epidemiologic linkage between a transfusion recipient and a blood
donor. A confirmed case of clinical babesiosis, including those observed in blood donors or
transfusion recipients, demonstrates clinical signs or symptoms of disease coupled with direct
visualization of intraerythrocytic parasites, a positive nucleic acid test, or detection of organisms
in an inoculated animal (i.e., confirmatory laboratory evidence). A probable clinical case
demonstrates serologic confirmation of babesiosis with objective clinical evidence of disease (i.e.,
fever, anemia, or thrombocytopenia). In the case of TTB, the evidence may include an implicated
blood donor or recipient who has confirmatory laboratory evidence of infection in the absence of
signs and symptoms or who has serologic confirmation and may or may not have subjective
clinical evidence of infection (i.e., chills, sweats, headache, myalgia, or arthralgia), but does not
have any objective clinical evidence of disease.
In states and territories in which babesiosis is reportable, all potential cases should be reported,
including reactive test results from donors and recipients identified as part of IND screening or
testing implemented after FDA licensure, and suspected TTB cases. The latter should also be
reported to the appropriate health department even in states where the condition is not yet
reportable, as the health department may be able to assist with the investigation.
TTB Cases
A comprehensive review article from the Centers for Disease Control and Prevention (CDC)
compiled data on 159 TTB cases caused by B. microti in the US from 1979 (i.e., first reported TTB
case) to 2009.2 These cases were ascertained mostly through passive surveillance, and the authors
believe this is an underestimate of the total number of actual cases during this time. Most cases
were discovered as a result of the recipient developing clinical symptoms; a minority of cases were
detected through recipient tracing from an infected donor (i.e., look-back). Recognized cases
included neonates, the elderly, asplenic patients, and those with an attenuated immune response
due to cancer and other hematologic disorders.
 All-cause mortality rate was 18% (28 cases).
 Median recipient age was 65 years (range, <1 to 94 years) with 18 (11%) cases occurring in
infants and 106 (68%) cases in recipients >50 years of age.
 The most common diagnoses/procedures reflected groups at high risk for receiving Red Blood
Cell (RBC) transfusion: hematologic disorders [e.g., hematologic cancer (n=14), sickle cell
disease (n=11), thalassemia major (n=7), and other (n=7)]; 22 patients with cardiovascular
disease and procedures, and 19 patients with gastrointestinal bleeding or procedures.
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Thirty-two recipients (20%) had undergone surgical splenectomy, either in the past (17 cases),
in the peritransfusion period (e.g., postrauma transfusion and splenectomy) (12 cases), or >1
month after transfusion (3 cases).
The median interval from transfusion to onset of clinical symptoms was 37 days (range, 11176 days) and the median interval from symptom onset to diagnosis was 6 days (range, 0-84
days).
Transfusion of RBC components accounted for 155 of the 159 cases (97%).
Transmission occurred throughout the RBC storage period (e.g., up to 40 days) and from
leukoreduced, irradiated, and frozen-deglycerolized RBC units.
Four cases were attributed to whole-blood-derived platelets, no cases from apheresis platelets
or plasma.
Cases were linked to donations made in all 12 months, with peak transmission occurring from
July to October.
Nearly 90% of cases were observed in the seven states where B. microti is endemic (i.e., CT,
MA, MN, NJ, NY, RI, and WI).
Nineteen cases (13%) occurred in states where Babesia is not endemic and were attributed to:
 RBC units collected in a Babesia-endemic area were shipped to a nonendemic area.
 A donor from a Babesia-endemic area donated while visiting a nonendemic area.
 A donor from a nonendemic area acquired the infection while visiting an area where
Babesia was endemic.
Of the total number of cases reported, 77% were reported from 1999 to 2009, suggesting a
rapid increase in frequency and/or better surveillance for TTB.
Information for Clinicians
Clinical Manifestations
Whether transmitted by ticks or blood transfusion, infection with B. microti can range from
asymptomatic to fulminating disease resulting in death. The incubation period from tick exposure
to symptoms can range from 1 week to several months, but usually is 1 to 4 weeks.1 In contrast,
the median interval from transfusion to symptoms in one large case series was 37 days, with a
range of 11 to 176 days.2
In healthy persons, B. microti infection is often asymptomatic or mild. Clinical manifestations
commonly include fever (as high as 105.6 F), chills, sweats, headache, malaise, myalgia, and other
nonspecific flu-like symptoms.1 Accompanying laboratory findings include hemolysis, hemolytic
anemia, and thrombocytopenia. Symptoms generally resolve in a few weeks, but subclinical
infection may persist for months to more than a year without treatment. The risk for symptomatic
infection and complications is increased among neonates; the elderly; those with an attenuated
immune response due to cancer, HIV infection, chronic heart, lung, or liver disease; treatment with
immunosuppressive drugs; and especially those with anatomic or functional asplenia (especially
as a result of hemoglobinopathy). These risk factors are common among transfusion recipients.
Complications of babesiosis may include hemodynamic instability, acute respiratory distress
syndrome, severe hemolysis, disseminated intravascular coagulation, renal dysfunction, hepatic
compromise, congestive heart failure, and death. Immune dysregulation, including the stimulation
of autoantibodies that cross-react with similar antigens on erythrocytes, has been reported from
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both community-acquired babesiosis and TTB. These cases of autoimmunity often result in severe
hemolysis.8
Among hospitalized patients, fatality rates range from 6% to 9%, with rates as high as 21% for
immunocompromised patients. Persons who have asymptomatic infection or resolution of
symptoms may have low-level parasitemia for weeks to months, sometimes for longer than a year.
Asymptomatic parasitemia in potential blood donors presents the opportunity for transfusion
transmission, as well as for the appearance or recrudescence of symptoms in chronically infected
persons who become immunosuppressed.9
Babesiosis cannot be distinguished from other infections solely on the basis of signs and
symptoms; diagnostic testing is required. See Appendix B. The presence of an unexplained febrile
illness, especially when accompanied by hemolytic anemia, should prompt consideration of
babesiosis, especially for persons who live or visit Babesia-endemic areas or have been recently
transfused.
Treatment
Oral atovaquone with azithromycin for ≥7 to 10 days is an effective, readily available, and welltolerated treatment.10 The combination of quinine and clindamycin for a similar duration has been
recommended for treatment of symptomatic babesiosis, but can elicit side effects. Illness may
persist in severely immunocompromised patients, necessitating additional courses of treatment.
Red cell exchange transfusion is used as adjunctive therapy for life-threatening babesial infection
(e.g., parasitemia >10% or severe hemolysis) with dramatic improvements reported in some cases
with severe hemolysis.8, 11
Managing Potential TTB Cases
Infected Recipient
 The identification of recipients with TTB requires physicians who are well educated on, and
aware of, the risks of TTB. The subsequent investigation is the collaborative responsibility of
the hospital transfusion service, collection facilities, and the patient’s physician(s). Donors,
who are assumed to have been asymptomatic at the time of donation, may exhibit symptoms
after donation and receive a subsequent diagnosis of babesiosis (weeks to months following
donation) that needs to be reported promptly to the collection facility. Similarly, transfusion
services with a suspected TTB case must inform the blood center to facilitate donor evaluation
and control of in-date cellular components from suspect donors. Upon suspicion of TTB,
confirmation of the diagnosis and infecting species in the recipient is critical (including
exclusion of malaria), and whenever possible should be accomplished by direct detection [i.e.,
smear, polymerase chain reaction (PCR), animal inoculation]. When the patient resides in a
Babesia-endemic area, it is important to conduct a thorough evaluation of risk factors, and test
pretransfusion samples whenever available, to exclude the possibility of preexisting infection.
The type of sample and sample storage conditions may influence the suitability of these
samples to provide accurate test results, thereby affecting whether these tests can be used to
exclude donors as possible sources of infection.
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Generally, the incubation period for reported TTB cases is similar to or longer than that for
tick-borne infection. In rare instances (e.g., sickle cell patients) the incubation period can be
considerably longer, extending to several months.1,12
 Reporting TTB cases to the authorized state or local health department (see above under
“Babesiosis Case Reports”) may assist with the case investigation, as the health department
might have access to useful surveillance information that could be of assistance in donor
follow-up.
 The CSTE/CDC surveillance case definition, used for states to notify the CDC of cases, is
available as part of the National Notifiable Diseases Surveillance System at:
http://wwwn.cdc.gov/NNDSS/script/casedef.aspx?CondYrID=617&DatePub=1/1/2011
Case Investigation and Look-Back
 Typically, babesiosis is diagnosed in a transfused recipient and, if the clinician recognizes a
temporal relationship to transfusion, TTB is suspected. Investigations of credible reports of
TTB require evaluation of the donors whose cellular products were transfused.
 With confirmation of babesiosis in the recipient, an investigation is initiated by the transfusion
service with immediate reporting of the available data (e.g., recipient clinical history and
exposure history, other pertinent risk factors, laboratory studies, and the identification of
transfused components) to the collection facility.
o The case report should be evaluated to ascertain the likely window of potential transfusion
transmission. All donors associated with cellular products transfused to the recipient within
this window should be contacted for an interview regarding potential exposures, signs, and
symptoms, and asked to return for follow-up testing. Babesia antibody tests are optimal for
use in follow-up testing. Some investigational protocols use both antibody and DNA testing
by PCR to investigate suspect donors (see below).
 Reactive serology is consistent with either current or prior infection, but a positive
result alone does not provide conclusive evidence that the donor is the cause of the
transfusion transmission. Nevertheless, it is necessary to indefinitely defer this donor
as presumptively infected. Further, investigation of cases in which large numbers of
donors from Babesia-endemic areas with high seroprevalence for B. microti may result
in coincidentally positive results unrelated to the donor’s involvement in the case.
 In one investigational testing program, PCR has demonstrated that nearly 50% of
implicated donors are PCR positive for 2 to 7 months following the implicated
donation, including one PCR-positive/seronegative donor. Negative PCR test results
do not exclude prior or ongoing infection.
 In research settings, PCR also may provide a source of nucleic acid for subsequent
molecular studies that can be useful for establishing donor/recipient linkage in TTB
cases.
o If archived donor specimens are available for testing from the index or prior donations,
they can be useful. However, negative results do not exclude prior or current infection due
to potential sample dilution and sub-optimal storage conditions that may not maintain
detectable analyte concentrations.
 The medical director should evaluate the number of donors involved, determine and prioritize
at-risk donors (e.g., red cell donors, those from Babesia-endemic areas), then retrieve and
quarantine relevant in-date cellular components from appropriately vetted suspect donors
while the investigation is ongoing.
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Implicated donors of cellular products (positive for antibody and/or DNA) are indefinitely
deferred and referred to a physician for evaluation. The physician should receive all relevant
test results. There is no current protocol for reentry of implicated donors deferred for either a
history of babesiosis or reactive test results.
Donors with negative test results can be cleared and components may be (re)distributed for
transfusion, unless there are other reasons to suspect the donor (e.g., recipient with no risk for
tick-borne exposure); the donor is either the only donor or the only donor from a Babesiaendemic area whose products were transfused.
At the completion of the investigation, the medical director should determine if there is
sufficient evidence to implicate a specific donor or donors in the case. If there is such a
donor(s), other donors who have not yet been fully evaluated (for example, because they could
not be located or have not complied with requests for blood samples) may be cleared by the
medical director from further suspicion, based on available evidence.
Look-back and recipient notification:
o Currently there are no requirements for look-back to identify potentially infected recipients
of prior donations from donors implicated in TTB; however, some recipients may benefit
from this information.
 The existence of clusters of infection with Babesia in the US suggests look-back may
be useful for identifying other transmissions.
 At a minimum, recipients of cellular components from the index or subsequent
donations of the implicated donor should be investigated.
 Current investigational screening methods associated with IND protocols define the
period during which prior donations from implicated donors should be investigated.
Mitigation Strategies Including Donation Screening Results
Donor History Question and Deferral Due to a History of Babesiosis
The increasing incidence of TTB has provided impetus for the development of interventions to
reduce TTB. The only interventions implemented specifically to prevent TTB include a donorscreening question regarding a “history of babesiosis” and selective avoidance of blood collections
in some areas of relatively high Babesia endemicity.3 The high numbers of TTB cases suggest that
the use of a babesiosis history question is largely ineffective.
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The 29th edition of AABB Standards for Blood Banks and Transfusion Services requires the
indefinite deferral of a donor with a history of babesiosis, as noted above [Reference Standard
5.4.1A(11)].13
Similarly, a donor implicated in a TTB case should be considered equivalent to a donor with a
history of babesiosis and indefinitely deferred. This is consistent with Reference Standard
5.4.1A(11).
Investigational testing protocols (see below) require all donors with reactive or inconclusive
test results to be indefinitely deferred. There is no reentry process for donors who have been
implicated in TTB cases (by virtue of positive research or investigational tests) or for those
donors who have been deferred due to a reactive research or reactive/inconclusive
investigational test result.
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Donation Screening Under Research or IND Protocols
Several centers in Babesia-endemic areas of the US have evaluated research tests or implemented
testing performed under IND protocols. Research studies have established baseline seroprevalence
data, the impact of look-back (i.e., recipient tracing) investigations, and potential TTB mitigation
strategies.14-17 However, published research studies have been relatively small and lack methods
to differentiate true-positive from false-positive results. IND-related protocols were designed to
evaluate the performance characteristics of nucleic acid testing (NAT) and serology-based assays,
to assess their ability to prevent or reduce TTB, and to determine the prevalence and incidence of
infection in selected Babesia-endemic areas. Results of these studies will enable the development
of policy assessing the value of each test, the level of sensitivity required for each test, as well as
if, when, and where to apply them. Additional considerations will include cost-effectiveness of
testing algorithms and the willingness of hospitals to pay for testing.18 Results of investigational
testing have been published, summarized in the latest version of the Babesia EID Fact Sheet, and
presented at the 2013 AABB Annual Meeting. Updated highlights are presented below.
1. Results of repository testing using investigational tests
 A recent American Red Cross study of 13,269 linked repository donation samples tested
by investigational real-time PCR and arrayed fluorescence immunoassay (AFIA) using a
cutoff of 1:64 found rates of seropositivity of 0.025% in low-risk areas (AZ, OK), 0.12%
in moderate-risk areas (MN, WI) with 2/4,167 (0.05%) antibody and DNA positive, and
0.75% in high-risk areas (highly endemic counties in CT, MA) with 5/5,080 (0.1%)
antibody and DNA positive. All positive samples were confirmed by PCR and/or Western
blot in index or follow-up samples.19
 A peptide-based enzyme immunoassay (EIA) under IND protocol (Immunetics, Boston,
MA) was assessed by New York Blood Center and Blood Systems, Inc., in an unlinked
study of 15,000 donors from three geographic areas: Suffolk County (NY) representing a
high Babesia-endemic area, New York City serving as a low Babesia-endemic area, and
AZ designated as the nonendemic area.20 Donor results and those from 72 clinical cases of
laboratory-confirmed babesiosis were compared by the investigational EIA (see table
below). Results of EIA testing were compared to the results of a research-based
immunofluorescence assay (IFA) and a research-based, real-time PCR. Only one EIA
repeat-reactive sample was PCR positive; this sample was from the high Babesia-endemic
area. No additional results were provided to clarify the higher reactivity rates observed in
EIA versus IFA testing.
Study samples
EIA repeat reactive (%)
IFA+ at a 1:64 cutoff (%)
High Babesia-endemic,
Suffolk Co., NY
54 (1.08)
18 (0.36)
Low-endemic, NYC
37 (0.74)
3 (0.06)
Non-endemic, AZ
21 (0.42)
1 (0.02)
Clinical cases
71 (95.9)
71 95.9)
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2. Prospective investigational screening
 Rhode Island Blood Center is using a selective testing algorithm under an IND protocol
with AFIA (1:128 cutoff) and real-time PCR assays (IMUGEN, Norwood, MA) to
maintain an inventory of test-negative blood components for transfusion to high-risk
patients (i.e., neonates, pediatric patients with hemoglobinopathies). A preliminary
published report from this IND study revealed 26/2113 (1.23%) antibody positive; one
donor had an indeterminate PCR result (0.05%). No reported cases of transmission
occurred with any B. microti-screened units transfused to the targeted patients (0/787
units).21 Unpublished data from July 10 through February 2014 for 9,134 tested units show
67 (0.73%) were antibody positive, 1 (0.01%) was PCR and antibody positive, 2 (0.02%)
were PCR indeterminate, and 2 (0.02%) showed nonspecific fluorescence. No reported
cases of TTB occurred with any B. microti-screened units transfused to the targeted patients
(0/4,347) or to any patient who received tested units (0/9,058). In contrast, during this same
period there have been 11 cases of TTB associated with units not screened for B. microti
from 351,796 allogeneic donations, yielding an observed TTB risk of 1:32,000.
 Another IND study from the American Red Cross reported testing 84,209 donations as part
of product release during 2012-2014 (through April 30) in endemic counties of CT, MA,
MN, and WI using the investigational AFIA (1:128 cutoff) and real-time PCR assays
(IMUGEN).22 All positives were confirmed by PCR and/or Western blot positivity in index
or follow-up samples. Preliminary data include 331 (0.39%) reactive donations with 46
reactive by both assays (including one antibody positive/PCR-inconclusive donation that
was PCR positive by a more sensitive confirmatory method), 277 with antibody reactivity
only (including 10 antibody-positive/PCR-negative donations that were PCR positive by a
more sensitive confirmatory method), and eight that were DNA-positive only (windowperiod rate of 1:10,500). PCR-positive donations had parasite loads of 9 to 3 million
piroplasms/mL with 19/31 (61%) infectious in hamsters; an additional 2/33 antibody-only
positive donations were infectious in hamsters. Since the initiation of screening in JuneJuly 2012 through April 30, 2014, no cases of TTB from screened units have occurred
whereas 18 cases of TTB associated with unscreened units have occurred throughout the
American Red Cross system. Positive donors associated with TTB from unscreened units
were identified in CA (donor exposure in ME), CT, MA, MN, NH, and NJ. When restricted
to the 10 counties involved in the IND protocol, a comparison of TTB cases attributable to
unscreened vs screened units during the IND period approached significance (10 TTB
cases/200,488 unscreened units vs 0/59,848; odds ratio 6.3; p=0.07) and demonstrates an
observed residual TTB risk of 1:20,000 transfused units in Babesia-endemic areas.
See Appendix C for additional data from other prevalence studies and from look-back
investigations.
Other Considerations
Several other approaches to mitigating risk have been investigated with varying degrees of success.
Some approaches such as leukoreduction are largely ineffective, while newer technologies
including pathogen inactivation/reduction have demonstrated feasibility, but remain unlicensed in
the US.
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1. Donor screening risk-factor questions
Several follow-up studies of positive donors to identify risk factors associated with
infection have been performed.17 Common risk factors include tick exposure, proximity to
woods and deer, and outdoor activities (e.g., hiking, gardening). The potential use of a tick
exposure question was previously explored in a research study using IFA and EIA. No
differences in the seroprevalence of B. microti were observed for donors reporting tick
bites compared to control donors.23 On occasion, donors may provide postdonation
information on tick exposure, recent diagnosis of Lyme disease, etc. In these instances,
appropriate actions are left to local policies and/or the discretion of the medical director.
2. Leukoreduction/gamma irradiation
Given that babesial parasites are intraerythrocytic, leukoreduction will likely have minimal
to no impact on transmission. This conclusion is supported by reports of TTB cases
associated with leukoreduced blood products.6 Similarly, the occurrence of TTB cases
associated with gamma irradiated products suggests this approach is also ineffective.24
3. Pathogen inactivation/reduction
Pathogen inactivation (amotosalen + ultraviolet light) and pathogen reduction (riboflavin
+ ultraviolet light) have been shown to be effective at inactivating/reducing B. microti
parasites in platelet and plasma products inoculated with infected hamster erythrocytes.25,26
Recent studies have also demonstrated the efficacy of pathogen reduction in whole blood
(including RBC units), but at lower levels compared to platelet and plasma products.27
However, to date neither approach has been licensed by the FDA for use in the US.
Critical Issues That Require Further Consideration
 If implemented, in what geographic regions will testing occur?
o In July 2010, the FDA Blood Products Advisory Committee supported the concept
of regional testing, but it is not clear if testing would be limited to the seven states
where Babesia is endemic or if it will include other states judged to be at lower risk.
 What tests should be used and when?
o Current options used under IND protocols include: antibody only, NAT only, or
antibody and NAT.
o If NAT is implemented, should it be used seasonally or year-round?
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Which patients should receive tested blood products: high-risk patients only (e.g.,
neonates, pediatric patients with hemoglobinopathies) or all patients?
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If the FDA licenses an assay, will it also mandate testing?
o Given constrained reimbursement polices, will hospitals be able to pay for blood
products that have been tested before such tests are mandated?
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During the IND phase, will testing capacity meet demands?
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Key Points
1. Transfusion-transmitted babesiosis (B. microti) poses a significant threat to patients. There
is significant risk at varying levels in at least seven states (CT, MA, MN, NJ, NY, RI, and
WI), but some risk is also present in other states.
2. Transfusion-transmission has been documented in nonendemic areas due to several factors
including donor travel to high-risk areas and widespread distribution of blood collected in
Babesia-endemic areas across the US.
3. Although seasonal variation in incidence and TTB occur, infectious donors and TTB have
been documented year-round.
4. Babesiosis, including TTB, is now nationally notifiable, but is not reportable in every state.
5. TTB is responsible for 38% of transfusion-related infectious fatalities reported to the FDA
in transfusion recipients; this is the highest percentage among all infectious agents.
6. Patient susceptibility varies and cannot be predicted accurately, but the young, old (>50
years old), asplenics, and those with attenuated immune responses are at greatest risk for
severe complications from TTB.
7. Babesia has been prioritized as an agent with a critical need for the development and
implementation of an intervention to reduce the incidence of TTB.
8. Intervention methods to reduce TTB incidence currently in place, including donor
questioning or restricted collection areas, are ineffective.
9. No FDA-licensed testing method to reduce TTB incidence is available.
10. IND testing methods, including both antibody and nucleic acid tests, have demonstrated
encouraging results.
Recommendations
1. Hospitals and blood centers in Babesia-endemic areas should consider what interventions
are available and may be appropriate to reduce the risk of TTB.
2. Hospitals and/or blood centers interested in testing should contact an IND sponsor.
3. Hospitals and blood centers should fully investigate and report all cases of TTB.
References
1.
Vannier E, Krause PJ. Human babesiosis. N Engl J Med 2012;366:2397-407.
2.
Herwaldt BL, Linden JV, Bosserman E, et al. Transfusion-associated babesiosis in the
United States: A description of cases. Ann Intern Med 2011;155:509-19.
3.
Leiby DA. Transfusion-transmitted Babesia spp.: Bull’s-eye on Babesia microti. Clin
Microbiol Rev 2011;24:14-28.
4.
Food and Drug Administration. Fatalities reported to FDA following blood collection and
transfusion: Annual summary for fiscal year 2012. Silver Spring, MD: CBER Office of
Communication, Outreach, and Development, 2012. [Available at:
http://www.fda.gov/BiologicsBloodVaccines/SafetyAvailability/ReportaProblem/Transfu
sionDonationFatalities/ucm346639.htm(accessed June 2, 2014).]
5.
Stramer SL, Hollinger FB, Katz LM, et al. Emerging infectious disease agents and their
potential threat to transfusion safety. Transfusion 2009;49 Suppl 2:1S-29S.
Page 10 of 16
6.
Tonnetti L, Eder AF, Dy B, et al. Transfusion-transmitted Babesia microti identified
through hemovigilance. Transfusion 2009;49:2557-63.
7.
Centers for Disease Control and Prevention. 2013 national notifiable infectious
conditions. Babesiosis. Atlanta, GA, 2013. [Available at:
http://wwwn.cdc.gov/nndss/script/conditionsummary.aspx?CondID=24 (accessed
January 10, 2014).]
8.
Herman JH, Ayache S, Olkowska D. Autoimmunity in transfusion babesiosis: A spectrum
of clinical presentations. J Clin Apher 2010;25:358-61.
9.
Krause PJ, Gewurz BE, Hill D, et al. Persistent and relapsing babesiosis in
immunocompromised patients. Clin Infect Dis 2008;46:370-6.
10.
Krause PJ, Lepore T, Sikand VK, et al. Atovaquone and azithromycin for the treatment of
babesiosis. N Engl J Med 2000;343:1454-8.
11.
Powell VI, Grima K. Exchange transfusion for malaria and Babesia infection. Transfus
Med Rev 2002;16:239-50.
12.
Cirino CM, Leitman SF, Williams E, et al. Transfusion-associated babesiosis with an
atypical time course after nonmyeloablative transplantation for sickle cell disease. Ann
Intern Med 2008;148:794-5.
13.
Levitt J, ed. Standards for blood banks and transfusion services. 29th edition. Bethesda,
MD: AABB, 2014:63.
14.
Johnson ST, Cable RG, Tonnetti L, et al. Seroprevalence of Babesia microti in blood
donors from Babesia-endemic areas of the northeastern United States: 2000 through 2007.
Transfusion 2009;49:2574-82.
15.
Johnson ST, Cable RG, Leiby DA. Lookback investigations of Babesia microtiseropositive blood donors: Seven-year experience in a Babesia-endemic area. Transfusion
2012;52:1509-16.
16.
Johnson ST, Van Tassell ER, Tonnetti L, et al. Babesia microti real-time polymerase chain
reaction testing of Connecticut blood donors: Potential implications for screening
algorithms. Transfusion 2013;53:2644-9.
17.
Leiby DA, Johnson ST, Won KY, et al. A longitudinal study of Babesia microti infection
in seropositive blood donors. Transfusion 2014 (in press). DOI: 10.1111/trf.12622.
18.
Simon MS, Leff JA, Pandya A, et al. Cost-effectiveness of blood donor screening for
Babesia microti in endemic regions of the United States. Transfusion 2014;54:889-99.
Page 11 of 16
19.
Moritz ED, Winton CS, Johnson ST, et al. Investigational screening for Babesia microti in
a large repository of blood donor samples from nonendemic and endemic areas of the
United States. Transfusion 2014 (in press). DOI: 10.111/trf.12693.
20.
Levin AE WP, Erwin JL, Cyrus S, et al. Determination of seroprevalence of Babesia
microti (Bm) in endemic and non-endemic blood donor populations using an
investigational ELISA (abstract). Transfusion 2013;53 (Suppl.):42A-3A.
21.
Young C, Chawla A, Berardi V, et al. Preventing transfusion-transmitted babesiosis:
Preliminary experience of the first laboratory-based blood donor screening program.
Transfusion 2012;52:1523-9.
22.
Moritz E, Winton C, Townsend RL, et al. Extended Babesia microti investigational
screening studies: Implications for transfusion-transmitted Babesiosis (TTB). 2014 AABB
abstract (in press).
23.
Leiby DA, Chung AP, Cable RG, et al. Relationship between tick bites and the
seroprevalence of Babesia microti and Anaplasma phagocytophila (previously Ehrlichia
sp.) in blood donors. Transfusion 2002;42:1585-91.
24.
Lux JZ, Weiss D, Linden JV, et al. Transfusion-associated babesiosis after heart transplant.
Emerg Infect Dis 2003;9:116-9.
25.
Grellier P, Benach J, Labaied M, et al. Photochemical inactivation with amotosalen and
long-wavelength ultraviolet light of Plasmodium and Babesia in platelet and plasma
components. Transfusion 2008;48:1676-84.
26.
Tonnetti L, Proctor MC, Reddy HL, et al. Evaluation of the Mirasol pathogen [corrected]
reduction technology system against Babesia microti in apheresis platelets and plasma.
Transfusion 2010;50:1019-27.
27.
Tonnetti L, Thorp AM, Reddy HL, et al. Riboflavin and ultraviolet light reduce the
infectivity of Babesia microti in whole blood. Transfusion 2013;53:860-7.
Page 12 of 16
Appendix A
Epidemiology of Human Babesiosis
Human babesiosis is a tick-borne zoonosis caused by intraerythrocytic protozoan parasites of the
genus Babesia. Babesia parasites also can be transmitted by blood transfusion, which has been
documented for B. microti and B. duncani.1, 2
In the eastern US, B. microti is transmitted by Ixodes scapularis, commonly known as the blacklegged or deer tick, which also is the vector for Lyme disease (Borrelia burgdorferi), human
granulocytic anaplasmosis (Anaplasma phagocytophilum), and several other pathogens.3 Tickborne transmission of B. microti to humans is regional and seasonal. It is most common in the
Northeast and is widespread in coastal areas of CT, MA, NJ, NY, and RI, and is expanding into
coastal ME and NH A region of significant but lower risk is in the upper Midwest (MN and WI).
Although I. scapularis is common throughout the eastern US, there have been no documented B.
microti cases south of MD.
The primary reservoir host for B. microti is the white-footed mouse (Peromyscus
leucopus). Although white-tailed deer (Odocoileus virginianus) are not competent hosts for B.
microti, they play important roles in amplifying tick populations by providing a blood meal and
transporting ticks, thereby expanding their geographic distribution.
Tick-borne transmission occurs during late spring through summer (May through September)
because of the coincidence of tick and human activity; the parasite typically is spread by the
nymphal stage of I. scapularis, which is most active during warm months in brushy, wooded, or
grassy habitats. Most B. microti patients seek treatment during late June, July, and early- to midAugust, but new cases have been identified even in winter months due to exacerbation of a
subclinical infection that may have been acquired months earlier. The adult deer tick is a poor
vector of B. microti and thus people are rarely exposed during the fall and winter months.4
In 2012, the Centers for Disease Control and Prevention (CDC) was notified of 937 confirmed and
probable cases of babesiosis, with 96% (895) reported from the seven highest incidence states.5 In
2011, among reported cases, 62% were males, median age was 62 years (range <1-98 years), and
82% had symptom onset in June through August.6 Ten cases were reported to the CDC as
transfusion-transmitted babesiosis (TTB), but implicated donors were identified only in two of
these cases. As of January 10, 2014, 1,446 confirmed and probable cases were reported in 2013,7
but there is substantial lag in CDC notification due to the time it takes for case investigation and
classification.
Three cases of TTB due to B. duncani infection have been documented in CA and WA; however,
this parasite’s geographic range, tick vector, and reservoir host(s) are not known in the US.2
Page 13 of 16
Appendix A References
1. Herwaldt BL, Linden JV, Bosserman E, et al. Transfusion-associated babesiosis in the
United States: A description of cases. Ann Intern Med 2011;155:509-19.
2. Bloch EM, Herwaldt BL, Leiby DA, et al. The third described case of transfusiontransmitted Babesia duncani. Transfusion 2012;52:1517-22.
3. Leiby DA. Transfusion-transmitted Babesia spp.: Bull’s-eye on Babesia microti. Clin
Microbiol Rev 2011;24:14-28.
4. Vannier E, Krause PJ. Human babesiosis. N Engl J Med 2012;366:2397-407.
5. Centers for Disease Control and Prevention. Notice to readers: Final 2012 reports of
nationally notifiable infectious diseases. MMWR 2013;62:669-682. [Errata MMWR
2013;62:705].
6. Centers for Disease Control and Prevention. Summary of notifiable diseases — United
States, 2011. MMWR 2012;60:11-12.
7. Centers for Disease Control and Prevention. Notifiable diseases and mortality tables.
MMWR 2013;62:ND 719. [Available at:
http://www.cdc.gov/mmwr/pdf/wk/mm6250md.pdf (accessed January 10, 2014).]
Page 14 of 16
Appendix B
Diagnostic Testing Options for Babesiosis




Commercial options for diagnostic testing are limited. No Food and Drug Administration
(FDA)-licensed blood donor screening assay or FDA-approved diagnostic test exists.
Diagnosis is based on direct examination of Giemsa- or Wright-stained blood smears for
intraerythrocytic parasites; IgM and IgG antibody detection by standard or automated IFA
[arrayed fluorescence immunoassay (AFIA); IMUGEN, Inc., Norwood, MA], (cut-off titers
vary with assay and lab), enzyme immunoassay (EIA) and Western blot; molecular methods
[polymerase chain reaction (PCR) tests have been developed using primers from conserved
regions of the Babesia 18S rRNA gene], and lastly animal inoculation. The sensitivity and
specificity of these techniques are highly variable.
Acute, symptomatic cases of babesiosis usually are diagnosed by detection of Babesia parasites
during review of blood smears.
o Differentiation of Babesia from Plasmodium (malarial) parasites requires an experienced
microscopist. Digital images of blood films may be submitted to DPDx, a telediagnostic
service provided by the Centers for Disease Control and Prevention (CDC) Division of
Parasitic Diseases and Malaria (http://www.dpd.cdc.gov/dpdx).
o Some Babesia species—including B. microti and B. duncani—cannot be distinguished
from each other by microscopy. If Babesia parasites are evident on a blood smear, but B.
microti PCR results are negative, additional molecular and/or serologic testing may be
required to identify the infecting Babesia
During subsequent stages of infection, parasitemia levels may be below the threshold for visual
detection, but might be detectable by PCR and/or animal inoculation.
o Detection of DNA by PCR in the absence of antibody may be indicative of a windowperiod infection, but should be confirmed by donor follow-up and repeat serology.
o Although PCR is more sensitive than blood-smear examination, negative results do not
preclude infection or infectivity.
o Molecular detection has been limited by low concentrations of circulating parasites in some
cases coupled with the relatively low input volume of blood tested.
Except for the early acute stage of infection (i.e., window period), serologic techniques provide
evidence of current or past infection. Seropositivity can persist for many months, sometimes
years, even after apparent resolution of infection.
o The gold-standard methodology is the IFA antibody test, which generally uses Babesiainfected hamster erythrocytes as the antigen source.1
o Because serologic testing is species specific, the pertinent antigen source must be used
(e.g., B. microti or B. duncani).
Appendix B Reference
1. Chisholm ES, Ruebush TK, 2nd, Sulzer AJ, et al. Babesia microti infection in man:
Evaluation of an indirect immunofluorescent antibody test. Am J Trop Med Hyg
1978;27:14-9.
Page 15 of 16
Appendix C
Donation Screening Under Research Protocols
Prevalence Studies Using Research Tests
 Seroprevalence by a research-based indirect immunofluorescence assay (IFA) in healthy blood
donors was reported as high as 2% in the Babesia-endemic areas of the Northeast and Upper
Midwest, areas that encompass approximately 16% of the US population. Areas of
hyperendemicity (up to 10% infected) in the general population have been reported in portions
of CT, MA, NY, and RI, particularly on offshore islands (e.g., Martha’s Vineyard and
Nantucket Island, MA; Shelter Island, NY).1
 One study of blood donors in MN reported 42 of 2150 (2%) positive for B. microti by researchbased IFA; one sample was also positive by research-based real-time polymerase chain
reaction (PCR). The study focused on donors residing in areas considered endemic for B.
microti. All positive donors reported extensive outdoor activities, many with tick exposure.2
 A limited study in the highly endemic areas of CT tested 1002 donors during the tick season
by research-based IFA and real-time PCR assays. Twenty-five (2.5%) donors were positive by
IFA and 3 (0.3%) positive by PCR. Among the PCR-positive donors, two were IFA positive,
while one was IFA negative and suggestive of a window-period infection.3
 The prevalence rates in the above studies are likely overestimates as false-positive results could
not be excluded.
Results from Look-Back
The infectivity of blood products from regions of high Babesia endemicity in CT during 1999 to
2005 was assessed by research-based IFA and real-time PCR screening of donors (i.e., before
investigational new drug studies).4 Recipient tracing and testing demonstrated that 12.7% of recipients who received a seropositive index or prior donation from a seropositive donor were Babesia
positive by IFA and/or PCR. Recipient positivity was primarily associated with transfusion of a
positive index component (50%) vs a prior donation from an infected donor (7.3%), and donors
who were PCR positive (33.3%) vs negative (2.9%). Seven of eight positive recipients received
RBC units while one received whole-blood-derived platelets; RBC age at the time of transfusion
ranged from 7 to 42 days, and the platelets at transfusion were 5 days old.
Appendix C References
1. Leiby DA. Transfusion-transmitted Babesia spp.: Bull’s-eye on Babesia microti. Clin
Microbiol Rev 2011;24:14-28.
2. Tonnetti L, Thorp AM, Deisting B, et al. Babesia microti seroprevalence in Minnesota
blood donors. Transfusion 2013;53:1698-705.
3. Johnson ST, Van Tassell ER, Tonnetti L, et al. Babesia microti real-time polymerase chain
reaction testing of Connecticut blood donors: Potential implications for screening
algorithms. Transfusion 2013;53:2644-9.
4. Johnson ST, Cable RG, Leiby DA. Lookback investigations of Babesia microtiseropositive blood donors: Seven-year experience in a Babesia-endemic area. Transfusion
2012;52:1509-16.
Page 16 of 16